9350(  2) - 02/05/02 11:40  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9350
                                                       Version: 2
                                                       Check-in Date: 05-Feb-2002
                                                                      11:40:01

1.Proposal Title:
Intergalactic HeII absorption in CSO 118 = HS 1157+3143
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2. Proposal For  3. Cycle
GO               11
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4. Investigators
                                                                                     Contact?
    PI: Dieter Reimers                    Universitat Hamburg, Hamburger Sternwarte
   CoI: Dr. Hans-Juergen Hagen            Hamburger Sternwarte                          Y
   CoI: Dr. Peter Jakobsen                Astrophysics Division, ESA/ESTEC              N
   CoI: Dr. David Tytler                  University of California                      N

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5. Abstract

We propose to observe the HeII Gunn-Peterson effect in the z = 3 quasar CSO 118,
which has been discovered in our SNAPSHOT survey to have a transparent line of
sight. The aim is in particular to extend our knowledge about HeII reionization
which has been observed to take place in the range z = 3.1 to z = 2.8. While
existing and future FUSE observations will cover the redshift range z < 2.9,
redshifts above 2.9 have been covered by HST with only 2 lines of sights.
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  Observations Description
  ------------------------

     We propose to take STIS low resolution G140L spectra covering the range 1150 -
     1700Angstrom with the aim to measure quantitatively the intergalactic HeII
     304Angstrom absorption in CSO 118. The flux level is 1 \cdot 10^-16 erg cm^-2
     s^-1 AA^-1 above the HeII edge. This yields an S/N = 12 in 23000 sec just above
     the HeII edge and guarantees mapping the proximity zone with good S/N. In
     addition we wish to detect further gaps in the HeII absorption and even a
     finite optical depth (Tau = 2, f_Lambda = 2 \cdot 10^-17) at z = 2.82 as found
     in Q 0302-003.

  Real Time Justification
  -----------------------

     For CSO 118 (Q 1157+3143) D. Tytler has taken a high S/N HIRES/Keck spectrum
     (cf. ApJ 512, L5).

  Calibration Justification
  -------------------------


  Additional Comments
  -------------------

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                                                9350(  2) - 02/05/02 11:40  - [  2]

TARGET LIST    Fixed Targets
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Tar|   Target   |         Target        |            Target              |Coord   | Radial |             Flux data
No |    Name    |       Description     |           Position             |Eqnx    |  Vel.  |
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1   CSO0118      GALAXY, QSO             RA= 12H 00M 06.19S +/- 0.08S,    J2000    Z=2.98   V = 16.1
                                         DEC=31D 26' 30.2"  +/- 1", PLATE                   B-V = 0.5
                                         -ID=01TE
    Coordinate Source: GSC_SURVEY_PLATE

                                                9350(  2) - 02/05/02 11:40  - [  3]

Visit: 01
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
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1        CSO0118     STIS/C ACQ     F28X50L MIRROR                                             1   4 S
                     CD             P
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2        CSO0118     STIS/F ACCUM   52X0.5  G140L    1425                                      1   2500 S
                     UV-MAM
                     A
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3        CSO0118     STIS/F ACCUM   52X0.5  G140L    1425                                      3   3000 S
                     UV-MAM
                     A
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                                                9350(  2) - 02/05/02 11:40  - [  4]

Visit: 02
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1        CSO0118     STIS/C ACQ     F28X50L MIRROR                                             1   4 S
                     CD             P
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2        CSO0118     STIS/F ACCUM   52X0.5  G140L    1425                                      1   2500 S
                     UV-MAM
                     A
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3        CSO0118     STIS/F ACCUM   52X0.5  G140L    1425                                      2   3000 S
                     UV-MAM
                     A
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                                                9350(  2) - 02/05/02 11:40  - [  5]

Visit: 03
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1        CSO0118     STIS/C ACQ     F28X50L MIRROR                                             1   4 S
                     CD             P
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2        CSO0118     STIS/F ACCUM   52X0.5  G140L    1425                                      1   2500 S
                     UV-MAM
                     A
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3        CSO0118     STIS/F ACCUM   52X0.5  G140L    1425                                      2   3000 S
                     UV-MAM
                     A
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                                                9350(  2) - 02/05/02 11:40  - [  6]

            Summary Form for Proposal  9350

  Item                         Used in this proposal
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  Apertures                    F28X50LP 52X0.5
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  Configurations               STIS/CCD STIS/FUV-MAMA
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  Opmodes                      ACQ ACCUM
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  Proposal Category            GO
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  Spectral Elements            MIRROR G140L
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  Target Names                 CSO0118
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  Wavelengths                  1425
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